Patent GB-506351-A (GB)
Title: Improvements in or relating to liquid pressure remote control systems
IPC: B64C25/22
Filed: 1937-11-25
Abstract: 506,351. Liquid pressure remote-control systems; valves. AUTOMOTIVE PRODUCTS CO., Ltd., and PARKER, S. M. Nov. 25, 1937, No. 32562. [Classes 69 (ii) and 135] A liquid pressure remotecontrol system for performing one or more primary services and one or more secondary services, comprises a pump delivering liquid under pressure directly to motor units, or to pressure accumulators supplying motor units, operating the main services, and also to pressure accumulators supplying motor units operating the secondary services, and a valve device operated by loss of liquid from the system to isolate from the pump the pressure accumulators supplying the motor units of the secondary services. A system for aircraft comprises, Fig. 1, double-acting jacks 2, 2 and 3, 3 for operating the retractable undercarriage and flaps respectively, under the control of a selector valve (i, which may be of the automatic self-return type described in Specification 480,180. A hydraulie locking device 25 is associated with the flap jacks 3. Accumulators 4, 5 supply liquid for operating brakes and guns, under the control of valves (not shown), the accumulators being provided with valves for byepassing them when fully charged, as e.g. in Specification 486,855. The pump 1 draws from a reservoir 7 and delivers through 11 to a valve 8, from which the liquid normally passes by lines 12, 15 to charge the accumulators 4, 5 and thence by double non-return valve unit 16 and line 17 to the selector valve 6, the return liquid passing by pipe 24 to the reservoir. The valve 8 is operated automatically by loss of liquid from the system and the pressure liquid from the pump then passes by line 13 to the unit 16 and thence only to the selector valve 6. Thus operation of the essential services is maintained despite a breakdown in that part of the system associated with the other services. A stand-by hand pump 26 delivers through a valve 31 operated at will either by line 33 to the selector valve 6 for operation of the primary services only, or by line 32 to the line 15 for charging the accumulators 4, 5, as well. The automatically operated valve 8 comprises, Fig. 2, a valve plunger 35 urged to one end position by a spring, but normally held in the other end position by a ball detent 53 acted on by a cam 57 on the pivot of a float 63 in the reservoir 7; if a break occurs in the system, the consequent loss of liquid therefrom causes a lowering of the level in the reservoir, the float thus falling and causing the detent 53 to release the valve. The return pipes from the selector valve and from the motor units of the secondary services are connected to stand pipes in the reservoir to prevent loss of liquid through said return pipes. In a modification, Fig. 4, the valve 81 is held in one end position against the action of the spring 92 by a detent 93 carried by a piston 94 ; the pump suction from the reservoir is through a stand pipe 101 ; when the liquid level in the reservoir falls, a float 106 closes the end of the stand pipe 101 and the piston 94 is drawn upwardly by the pump suction to release the valve 81 ; the pump now draws through standpipe 102, 98, 97 and ports 105 in the piston 94. A modified form of float, Fig. 5 (not shown) may be employed. The. primary services may, instead of being operated directly by the pump through a selector valve, be operated by accumulators charged by the pump as described above for the secondary services. A single device, such as a retractable undercarriage, may be operated normally by an accumulator or alternatively in an emergency by the pump direct. In a modification, Fig. 6, the undercarriage is operated by jacks 121 under the control of a selector valve 6 and supplied either by the pump 1 through 17 and non-return valve 126, or by an accumulator 122 through non-return valve 124 and a valve 125. The control rod of the valve 125 has a lost motion connection 127 with the hand lever 128 of the selector valve 6, the arrangement being such that when the selector valve 6 is operated to raise the undercarriage the lever 128 moves independently of the control rod and the valve 125 remains closed, so that the raising operation is carried out by pressure liquid coming directly from the pump 1. When the selector valve is operated to lower the undercarriage, however, the lever 128 engages the control rod and the valve 125 is opened, so that the pressure in the accumulator 122 assists that from the pump; owing to the provision of the non-return valves 124, 126, either the pump or the accumulator will effect lowering of the undercarriage despite a break in the pipes associated with the other. The valve 125 may be actuated independently of the valve 6, so that the accumulator pressure can also be used for raising the undercarriage. The pressure accumulators actuating the secondary services may be arranged in the return pipeline between the selector valve and the reservoir whereby the main services will have priority of operation if one is selected whilst one or more of the accumulators is partially discharged.